The following are key points to remember from these American College of Physicians (ACP) rapid, living practice points on the antibody response and role in conferring natural immunity after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection:

1. The ACP Scientific Medical Policy Committee developed these rapid, living practice points to summarize the current and best available evidence on the antibody response to SARS-CoV-2 infection, antibody durability after initial infection with SARS-CoV-2, and antibody protection against reinfection with SARS-CoV-2.
2. The widespread availability of SARS-CoV-2 antibody tests raises important questions for clinicians, patients, and public health professionals related to the appropriate use and interpretation of these tests.
3. Evidence from studies evaluating community prevalence in antibody response showed that patients develop an immune response after SARS-CoV-2 infection. This is evidenced by detectable IgA antibodies in most patients (low certainty), IgM in most patients (moderate certainty), IgG in nearly all patients (moderate certainty), and neutralizing antibodies in nearly all patients (low certainty).
4. At or around peak level, IgM, IgG, IgA, and neutralizing antibodies are estimated to be detectable in approximately 80%, 95%, 83%, and 99% of patients, respectively, after symptom onset or polymerase chain reaction (PCR)-confirmed infection.
5. Given that not all patients develop detectable antibodies early in the course of the infection and that the presence and levels may vary by patient and disease characteristics, antibody tests should not be used for the diagnosis of SARS-CoV-2 infection.
6. It is also important for clinicians and patients to keep in mind that SARS-CoV-2 antibody test results may be falsely positive due to cross-reactivity with antibodies of other coronaviruses.
7. However, for the purposes of estimating community prevalence of SARS-CoV-2 infection, antibody testing is a feasible option, keeping in mind that antibody levels peak roughly 3-5 weeks after symptom onset or PCR diagnosis.
8. The antibody prevalence and levels over time may vary by certain patient characteristics (for example, age, sex, and race/ethnicity) and disease factors (for example, presence of symptoms and severity) (low certainty).
9. Current evidence is uncertain to predict presence, level, or durability of natural immunity conferred by SARS-CoV-2 antibodies against reinfection (after SARS-CoV-2 infection).
10. Finally, given limited knowledge about the association between antibody levels and natural immunity, patients with SARS-CoV-2 infection and those with a history of SARS-CoV-2 infection should follow recommended infection prevention and control procedures to slow and reduce the transmission of SARS-CoV-2.

Editorial note: The underlined words above are ACP practice points 1-3.

Clinical Topics: COVID-19 Hub, Prevention

Keywords: Antibodies, Neutralizing, Antibody Formation, Coronavirus, COVID-19, Ethnic Groups, Immunity, Innate, Immunoglobulin A, Immunoglobulin G, Immunoglobulin M, Polymerase Chain Reaction, Primary Prevention, SARS-CoV-2

< Back to Listings